This invention relates to a process for hydrating dicyclopentadiene, i.e., tricyclo(5, 2, 1, 0.sup.2, 6)-deca3,8-diene, (hereinafter referred to as "DCPD" which is a registered trade-mark of Hitachi Chemical Co., Ltd.) to yield the corresponding alcohol, i.e., tricyclo(5, 2, 1, 0.sup.2,6)-3-decene-8 (or 9)-ol (hereinafter referred to as "DCPD-OH").
DCPD-OH is an alicyclic unsaturated secondary alcohol, and generally so-called as hydroxy dicyclopentadiene, which is used as a modifier for polyester resins, alkyd resins and the like.
Heretofore, DCPD-OH has been prepared by indirect hydration of DCPD by sulfuric acid. For example, there is disclosed a so-called sulfuric acid method in J. Am. Chem. Soc. 67, 723 (1945). The sulfuric acid method, however, has many defects as follows:
(1) Since 20 to 40% sulfuric acid is used, corrosion of the apparatus is remarkable. (2) Since sulfuric acid is mixed in the oil layer obtained by the reaction containing DCPD-OH, the purified DCPD-OH obtained by direct distillation of the oil layer contains a trace of sulfuric acid which makes the product easily colored. In order to avoid coloring of the product, the oil layer is neutralized with an alkali and washed. But these treatments produce a large amount of waste water. Thus a large amount of investment is necessary to avoid water pollution. (3) In the sulfuric acid method, since a stoichiometric amount of sulfuric acid is necessary for the starting DCPD, and since sulfuric acid should be used 2 to 4 times (by weight) as much as the starting DCPD if the concentration of sulfuric acid is 20 to 40%, a reaction kettle having a large volume should be used.
In addition, because of complicated procedures as mentioned above, the production cost of DCPD-OH is inevitably very high. Further if sulfuric acid is used as a catalyst, polymers are by-produced, which lowers selectivity for DCPD-OH. Therefore production of DCPD-OH by direct hydration with high selectivity and without causing water pollution has been desired in this industry.
On the other hand, in general, as catalysts for hydrating unsaturated compounds, there are known mineral acid catalysts such as phosphoric acid, boric acid, and their salts as well as sulfuric acid mentioned above, and heteropoly acid catalysts. The mineral acid catalysts are known to have such a defect as remarkable corrosion of the apparatus and there is the same problem in the production of DCPD-OH. It is known that the heteropoly acid catalysts can be used for the hydration of olefins having up to 4 carbon atoms, particularly for ethylene and propylene, from which the corresponding alcohols can be obtained in good yields. But if the number of carbon atoms of olefins become larger, for example in the case of diisobutylene and myrcene, reactions hardly proceed or no reactions take place even if the heteropoly acid catalysts are used.
But surprisingly, the present inventors have found that hydration reaction can be proceeded by a heteropoly acid in the case of DCPD having the norbornene skeleton having 10 carbon atoms and accomplished the present invention.